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High power impulse magnetron sputtering discharge (HIPIMS)
J. T. Gudmundsson 한국표면공학회 2012 한국표면공학회 학술발표회 초록집 Vol.2012 No.5
The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulses at low duty cycle and low repetition frequency while keeping the average power about 2 orders of magnitude lower than the peak power [1]. This results in a high plasma density, and high ionization fraction of the sputtered vapor, which allows better control of the film growth by controlling the energy and direction of the deposition species. This is a significant advantage over conventional dc magnetron sputtering where the sputtered vapor consists mainly of neutral species. The HiPIMS discharge is now an established ionized physical vapor deposition technique [2,3], which is easily scalable and has been successfully introduced into various industrial applications. An overview of the development of the HiPIMS discharge and the underlying mechanisms that dictate the discharge properties is given. The development and properties of the high power pulsed power supply will be discussed, followed by an overview of the measured plasma parameters in the HiPIMS discharge, the electron energy and density, the ion energy, ion flux and plasma composition, and a discussion on the deposition rate. Then a brief overview of the benefits and applications of the HIPIMS technique is given.
Farthest-polygon Voronoi diagrams
Cheong, O.,Everett, H.,Glisse, M.,Gudmundsson, J.,Hornus, S.,Lazard, S.,Lee, M.,Na, H.S. Elsevier 2011 Computational geometry Vol.44 No.4
Given a family of k disjoint connected polygonal sites in general position and of total complexity n, we consider the farthest-site Voronoi diagram of these sites, where the distance to a site is the distance to a closest point on it. We show that the complexity of this diagram is O(n), and give an O(nlog<SUP>3</SUP>n) time algorithm to compute it. We also prove a number of structural properties of this diagram. In particular, a Voronoi region may consist of k-1 connected components, but if one component is bounded, then it is equal to the entire region.
A fast algorithm for data collection along a fixed track
Cheong, O.,El Shawi, R.,Gudmundsson, J. North-Holland Pub. Co ; Elsevier Science Ltd 2014 Theoretical computer science Vol.554 No.-
Recent research shows that significant energy saving can be achieved in wireless sensor networks (WSNs) with a mobile base station that collects data from sensor nodes via short-range communications. However, a major performance bottleneck of such WSNs is the significantly increased latency in data collection due to the low movement speed of mobile base stations. In this paper we study the problem of finding a data collection path for a mobile base station moving along a fixed track in a wireless sensor network to minimize the latency of data collection. The main contribution is an O(mnlog@?n) expected time algorithm, where n is the number of sensors in the networks and m is the complexity of the fixed track.